RT Journal Article SR Electronic T1 Functional residual capacity measurements in healthy infants: ultrasonic flow meter versus a mass spectrometer JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 763 OP 768 DO 10.1183/09031936.04.00091504 VO 23 IS 5 A1 J.J. Pillow A1 H. Ljungberg A1 G. Hülskamp A1 J. Stocks YR 2004 UL http://erj.ersjournals.com/content/23/5/763.abstract AB Accurate, reproducible and portable bedside monitoring of lung volume could potentially facilitate the early recognition of both under and overinflation of the lungs in ventilated and nonventilated subjects. This study asked whether a prototype portable ultrasonic flow meter provided valid and reliable measurements of functional residual capacity (FRCUS) when compared to those obtained using a mass spectrometer (FRCMS) in nonventilated healthy infants. Paired, randomised measurements of FRCMS and FRCUS were obtained using the sulphur hexafluoride (SF6) multiple-breath washout technique in 23 healthy infants with a median (range) postnatal age of 34.6 (1.3–92.6) weeks and weight of 8.3 (3.9–11.7) kg. FRCUS was on average 5.7% (95% CI: 1.0–10.4%) less than FRCMS equating to a difference of approximately 1 mL·kg−1. The 95% limits of agreement (LA) between the two techniques were relatively wide (95% LA: −17.5% to 29%), although in keeping with previously reported within-patient variability for lung volume measurements. There was no significant difference between the within subject coefficient of variation for FRCMS (3.7%) and FRCUS (5.2%). The ultrasonic flow meter used in this study provides repeatable measurements of functional residual capacity in spontaneously breathing healthy infants that approximate those obtained during mass spectrometry. This research was supported by a Neil Hamilton Fairley NHMRC Postdoctoral Fellowship (J.J. Pillow), a European Respiratory Society Long Term Research Fellowship (H. Ljungberg), the Innovative Medizinische Forschung, University of Münster, Germany, and the Gesellschaft für Pädiatrische Pneumologie (G. Hülskamp) and Portex Ltd (J. Stocks). Research at the Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust benefits from R&D funding received from the NHS Executive.